Maximum Likelihood estimation

Suppose that a random variable Y has pdf:
f(y;a;b)=aby^(b-1)e^(-ay^(b))a)Find the maximum likelihood estimator for a assuming that b is known. b) Suppose a and b are both unknown. Explain how you would work out the two maximum likelihood estimators of a and b.

I honestly have no idea how to solve this... i have tried googling it but it wasnt not very helpfull. any help would be really appreciated.thanks

Suppose that a random variable Y has pdf:f(y;a;b)=aby^(b-1)e^(-ay^(b))a)Find the maximum likelihood estimator for a assuming that b is known. b) Suppose a and b are both unknown. Explain how you would work out the two maximum likelihood estimators of a and b.

I honestly have no idea how to solve this... i have tried googling it but it wasnt not very helpfull. any help would be really appreciated.thanks